方向性珪素鋼に対するSi-SiC系酸化防止剤の酸化防止機構
1988 年 74 巻 5 号 p. 855-862
詳細
1988 年 74 巻 5 号 p. 855-862
Antioxidation mechanism of a newly developed oxidation inhibitor of refractory powder mixture composed of SiO2, Si, SiC, synthetic mica, colloidal silica, surface active agent, and coking bond has been investigated.
During heating, Al2O3 is formed as a result of the decomposition by Si (metallic silicon) of mullite (3Al2O3·2SiO2) contained in refractory powder. Furthermore, the fine SiC powder is oxidized and changes gradually to a protective cristobalite-SiO2 (C-SiO2) layer which acts as an excellent diffusion barrier to oxygen from atmosphere. The protective C-SiO2 is not formed from the C-SiO2 which is added in the oxidation inhibitor but is formed through the oxidation process of the SiC.
On the other hand, Al2O3 which is formed by the decomposition of mullite becomes Al2O3·SiO2 in combination with SiO2. On the steel surface, however, Al2O3 becomes highly protective FeO·Al2O3or 3FeO·Al2O3·3SiO2 layer and, at the same time, it prevents the formation of a low melting point material such as fayalite (2FeO·SiO2).
It has been clarified that this oxidation inhibitor exhibits the excellent antioxidability due to superposed effect of above-mentioned reactions.
